I'm still trying to get over how awesome Google's 2014 Little Box Challenge was. Only a 2kW inverter, but one team (the Red Electronic Devils) managed a 14 cubic inch design. All the technical approaches are documented, as a part of the competition. A good number of extremely interesting ultra-high efficiency inverter designs!!

[1] https://ai.googleblog.com/2016/02/and-winner-of-1-million-li...